Referring to FIG. 1, an axial flow gas turbine 10 includes a compressor section 12, a combustion section 14 and a turbine section 16 arranged along a central axis 17. The compressor section 14 provides a compressed air flow to the combustion section 14 where the air is mixed with a fuel, such as natural gas, and ignited to create a hot working gas. The hot gas expands through the turbine section 16 where it is directed across rows of blades therein by associated vanes. As the hot gas passes through the turbine section 16, it causes the blades to rotate, which in turn causes a shaft to rotate, thereby providing mechanical work.
The gas turbine 10 further includes an exhaust cylinder section 18 located between the turbine section 16 and an exhaust manifold section 20. Referring to FIG. 2, an enlarged view of balloon section 2 of FIG. 1 is shown which depicts the exhaust cylinder 18 and exhaust manifold 20. The exhaust cylinder 18 includes an exhaust cylinder flange 22 that is attached to an exhaust manifold flange 24 of the exhaust manifold 20 at a flange interface 26. The exhaust cylinder 18 and exhaust manifold 20 include an exhaust diffuser 28 and a manifold diffuser 30, respectively, arranged along the central axis 17. Hot gas 21 leaving a last row of turbine blades in the turbine section 16 is directed through a flow path formed by the exhaust 28 and manifold 30 diffusers. The exhaust 28 and manifold 30 diffusers are spaced apart to form a circumferential diffuser gap 32 in order to allow for thermal expansion during operation of the gas turbine 10. In addition, an annular cavity 34 is formed between the exhaust cylinder 18 and the exhaust diffuser 28. It is desirable to avoid the entry, or recirculation, of hot gas 21 into the cavity 34 via the gap 32 since this would subject the exhaust cylinder 18 to excessive heat leading to the formation of cracks in the exhaust cylinder 18 and struts located between an inner ring and an outer case of the gas turbine 10.
Many gas turbines include a plurality of stiff metal plate seal segments known as baffle plates 36 that extend between the exhaust cylinder 18 and the exhaust diffuser 28. The baffle plates 36 serve to prevent or hinder the flow of hot gas 21 into the cavity 34. However, the baffle plates 36 tend to crack due to being subjected to thermal cycling and varying engine vibration levels that occur during typical operation of the gas turbine 10. Further, replacement of the baffle plates 36 is labor intensive and expensive. Referring to FIG. 3, gas turbines may alternatively utilize a plurality of relatively stiff metal finger plate seals 38 that extend across the gap 32 between the exhaust diffuser 28 and the manifold diffuser 30 in order to prevent or hinder the flow of hot gas 21 into the cavity 34. It has been found that the finger plate seals 38 also tend to crack due to thermal cycling and varying engine vibration levels.